1. Field of the Invention
The present invention relates to techniques for generating, as electronic information, classification codes regarding individual semiconductor chips tested in a wafer state. More particularly, the invention relates to an apparatus and a method for generating map data whereby some of the semiconductor chips rejected as defective in one test process but accepted as normal in another during multiple-process wafer testing are recovered as still useful in a way distinct from normally accepted chips.
2. Description of the Background Art
Conventional map data generating apparatuses typically have one storage area for accommodating a classification code regarding each of all chips making up a wafer. Final classification codes are obtained by overwriting the latest data with map data created in each process. Whereas chips judged flawless in all processes are accepted with no problem, those chips that were accepted as normal in a first process yet rejected as defective in an ensuing process are discarded traditionally because the final classification codes are written as defective. Some of the discarded faulty chips have been judged defective simply because of, say, relatively low operating speeds and have been highly likely to be still useful in a way different from normally accepted chips.
One disadvantage of the conventional map data generating apparatus is that once it judges semiconductor chips faulty, there is little possibility of having any of the discarded chips recovered as still useful in a way distinct from those judged normal.
It is therefore an object of the present invention to overcome the above and other deficiencies of the prior art and to provide an apparatus and a method for generating map data whereby some of the semiconductor chips rejected as faulty in one test process but accepted as normal in another during multiple-process wafer testing are recovered as still useful in a way different from normally accepted chips.
The above objects of the present invention are achieved by a map data generating apparatus described below. The apparatus includes probers for generating map data from execution of each of a plurality of processes constituting wafer tests. The apparatus also includes a cell controller for preserving the generated map data upon receipt thereof and for generating map data as final results in accordance with a classification code table which determines final classification codes by combining classification codes for each of the plurality of processes.
The above objects of the present invention are also achieved by a map data generating apparatus described below. The apparatus includes probers for generating map data from execution of each of a plurality of processes constituting wafer tests. The apparatus further includes a cell controller for preserving the generated map data upon receipt thereof and for generating final classification codes through logical operations on the basis of a classification code obtained before a current process and a classification code obtained in the current process.
The above objects of the present invention are achieved by a map data generating method described below. In the method, map data are generated from execution of each of a plurality of processes constituting wafer tests. The method includes a step of generating map data as final results in accordance with a classification code table which determines final classification codes by combining classification codes for each of the plurality of processes.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.